Wireless communication method and wireless communication terminal

ABSTRACT

Provided is a wireless communication terminal. The wireless communication terminal includes a transceiver configured to transmit/receive a wireless signal and a processor configured to control an operation of the wireless communication terminal. The transceiver receives a MAC frame including information on a plurality of wireless communication terminals that are to receive data from a base wireless communication terminal. The plurality of wireless communication terminals include the wireless communication terminal and receive data from the base wireless communication terminal based on the MAC frame.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal for setting a broadband link. Morespecifically, the present invention relates to a wireless communicationmethod and a wireless communication terminal for increasing datacommunication efficiency by expanding a data transmission bandwidth of aterminal.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using frequencies of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using frequencies of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses frequencies of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequencies of the 2.4 GHz band which aresignificantly congested and improves the communication speed up to amaximum of 54 Mbps by using an OFDM technology. However, the IEEE802.11a has a disadvantage in that a communication distance is shorterthan the IEEE 802.11b. In addition, IEEE 802.11g uses the frequencies ofthe 2.4 GHz band similarly to the IEEE 802.11b to implement thecommunication speed of a maximum of 54 Mbps and satisfies backwardcompatibility to significantly come into the spotlight and further, issuperior to the IEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11 ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of a radiointerface accepted by 802.11n, such as a wider radio frequency bandwidth(a maximum of 160 MHz), more MIMO spatial streams (a maximum of 8),multi-user MIMO, and high-density modulation (a maximum of 256 QAM).Further, as a scheme that transmits data by using a 60 GHz band insteadof the existing 2.4 GHz/5 GHz, IEEE 802.11ad has been provided. The IEEE802.11ad is a transmission standard that provides a speed of a maximumof 7 Gbps by using a beamforming technology and is suitable for high bitrate moving picture streaming such as massive data or non-compression HDvideo. However, since it is difficult for the 60 GHz frequency band topass through an obstacle, it is disadvantageous in that the 60 GHzfrequency band can be used only among devices in a short-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

Especially, as the number of devices using a wireless LAN increases, itis necessary to efficiently use a predetermined channel. Therefore,required is a technology capable of efficiently using bandwidths bysimultaneously transmitting data between a plurality of stations andAPs.

DISCLOSURE Technical Problem

An object of the present invention is to provide an efficient wirelesscommunication method and wireless communication terminal.

Another object of the present invention is to provide a wirelesscommunication method in which one wireless communication terminaltransmits data to a plurality of wireless communication terminalssimultaneously and a wireless communication terminal.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal receives a MAC frame including information on aplurality of wireless communication terminals that are to receive datafrom a base wireless communication terminal, and the plurality ofwireless communication terminals include the wireless communicationterminal and receive data from the base wireless communication terminalbased on the MAC frame.

At this time, the base wireless terminal may be any one wirelesscommunication terminal different from the plurality of wirelesscommunication terminals.

At this time, the transceiver may obtain a signaling field for signalinga signal including data transmitted to the plurality of wirelesscommunication terminals from a physical frame including data transmittedto the plurality of wireless communication terminals and obtaininformation on a frequency band allocated to the wireless communicationterminal from the signaling field.

At this time, the signaling field may include a plurality of fields, andeach of the plurality of fields may indicate a set of information on afrequency band allocated to each of the plurality of wirelesscommunication terminals.

At this time, the transceiver may decode a field indicating a set ofinformation on a frequency band allocated to the wireless communicationterminal, and stop decoding the plurality of fields.

In addition, the information on the frequency band may include bandwidthinformation indicating a bandwidth of the frequency band allocated tothe wireless communication terminal and Modulation & Coding Scheme (MCS)information indicating an MCS of a signal including data transmitted tothe wireless communication terminal.

In addition, the wireless communication terminal may further includegroup identifier information for identifying a group of wirelesscommunication terminals including the wireless communication terminalcorresponding to information signaled by the signaling field and streamnumber information indicating a space-time stream number transmittedthrough the frequency band allocated to the wireless communicationterminal.

In addition, the signaling field may include at least one of space-timeblock coding (STBC) information indicating whether STBC is applied to asignal including data transmitted to the wireless communicationterminal, convolution coding information indicating whether convolutioncoding is applied to a signal including data transmitted to the wirelesscommunication terminal, and extra symbol information indicating whetheran extra Orthogonal Frequency Division Multiplexing (OFDM) symbol isrequired by applying low-density parity-check code (LDPC) coding isapplied to a signal including data transmitted to the wirelesscommunication terminal.

In addition, the information on the frequency band may include a channelindex indicating a channel including the frequency band and asub-channel index indicating a sub-channel of the channel.

In addition, the information on the plurality of wireless communicationterminals may include an identifier for identifying each of theplurality of wireless communication terminals.

At this time, the information on the plurality of wireless communicationterminals may include information on a frequency band allocated to thewireless communication terminal.

At this time, the wireless communication terminal may further include achannel index indicating a channel including the frequency band and asub-channel index indicating a sub-channel including the frequency band,wherein the sub-channel is a sub-channel of the channel.

According to an embodiment of the present invention, a base wirelesscommunication terminal includes: a transceiver configured totransmit/receive a wireless signal; and a processor configured tocontrol an operation of the base wireless communication terminal,wherein the transceiver transmits a MAC frame including information on aplurality of wireless communication terminals that are to transmit datato the plurality of wireless communication terminals.

At this time, the base wireless terminal may be any one wirelesscommunication terminal different from the plurality of wirelesscommunication terminals.

At this time, the transceiver may transmit a physical frame includingdata and a signaling field to be transmitted to each of the plurality ofwireless communication terminals and the signaling field may signal asignal including the data.

At this time, wherein the signaling field may include a plurality offields, and each of the plurality of fields may include a plurality offields indicating a set of information on a frequency band allocated toeach of the plurality of wireless communication terminals.

In addition, the information on the frequency band may include bandwidthinformation indicating a bandwidth of the frequency band allocated tothe wireless communication terminal and Modulation & Coding Scheme (MCS)information indicating an MCS of a signal including data transmitted toeach of the plurality of wireless communication terminals.

In addition, the information on the frequency band may include a channelindex indicating a channel including the frequency band and asub-channel index indicating a sub-channel including the frequency band,and the sub-channel may be a sub-channel of the channel.

In addition, the information on the plurality of wireless communicationterminals may include an identifier for identifying each of theplurality of wireless communication terminals.

In addition, the transceiver may transmit a MAC frame for setting aNetwork Allocation Vector (NAV) of the plurality of wirelesscommunication terminals before transmitting the MAC frame.

In addition, the transceiver may transmit a MAC frame for setting aNetwork Allocation Vector (NAV) of the plurality of wirelesscommunication terminals after transmitting the MAC frame.

According to an embodiment of the present invention, an operating methodof a wireless communication terminal includes receiving a MAC frameincluding information on a plurality of wireless communication terminalsthat are to receive data from a base wireless communication terminalfrom the base wireless communication terminal, wherein the plurality ofwireless communication terminals include the wireless communicationterminal; and receiving data from the base wireless communicationterminal based on the MAC frame.

At this time, the base wireless terminal may be any one wirelesscommunication terminal different from the plurality of wirelesscommunication terminals.

An embodiment of the present invention provides an efficient wirelesscommunication method and wireless communication terminal.

Especially, an embodiment of the present invention provides a wirelesscommunication method and a wireless communication terminal in which anyone wireless communication terminal simultaneously transmits data to aplurality of wireless communication terminals.

Advantageous Effects

One embodiment of the present invention provides an efficient wirelesscommunication method and wireless communication terminal.

Especially, one embodiment of the present invention provides a wirelesscommunication method in which one wireless communication terminaltransmits data to a plurality of wireless communication terminalssimultaneously and a wireless communication terminal.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a view illustrating a wireless LAN system according to anotherembodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a view illustrating a process that a station sets an accesspoint and a link according to an embodiment of the present invention.

FIG. 6 is a view illustrating a structure of a poll frame according toan embodiment of the present invention.

FIG. 7 is a view illustrating a structure of a poll frame according toanother embodiment of the present invention.

FIG. 8 is a view illustrating a structure of a CH vector field in a pollframe according to an embodiment of the present invention.

FIG. 9 is a view illustrating a channel index in a frequency band of 5GHz according to an embodiment of the present invention.

FIG. 10 is a view illustrating a channel index in a frequency band of 5GHz according to another embodiment of the present invention.

FIG. 11 is a view illustrating a sub-channel index in a frequency bandof 20 MHz according to an embodiment of the present invention.

FIG. 12 is a view illustrating a sub-channel index in a frequency bandof 20 MHz according to another embodiment of the present invention.

FIG. 13 is a view illustrating a sub-channel index in a frequency bandof 20 MHz including a combination of non-contiguous sub-bands accordingto another embodiment of the present invention.

FIG. 14 is a view illustrating a preamble including sub-channelinformation according to an embodiment of the present invention.

FIG. 15 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

FIG. 16 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

FIG. 17 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

FIG. 18 is a view illustrating a CH vector field indicating acombination of non-contiguous sub-band channels according to anotherembodiment of the present invention.

FIG. 19 shows that an access point transmits data to a plurality ofstations using a poll frame.

FIG. 20 is a view illustrating that an access point transmits anRTS-to-Self frame and transmits data to a plurality of stations aftertransmitting a poll frame.

FIG. 21 is a view illustrating that an access point transmits a pollframe before transmitting an RTS frame and a CTS frame and transmitsdata to a plurality of stations.

FIG. 22 is a view illustrating that an access point transmits data to aplurality of stations using an M-RTS frame.

FIG. 23 is a view illustrating a physical frame according to anembodiment of the present invention.

FIG. 24 is a view illustrating a signaling field in a physical frameaccording to an embodiment of the present invention.

FIG. 25 is a ladder diagram illustrating operations of a first wirelesscommunication terminal and a second wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0143125 and Nos. 10-2015-0035127 filed in theKorean Intellectual Property Office and the embodiments and mentioneditems described in the respective applications are included in theDetailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STAS, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a radio medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2, duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STA7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STA7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a radio signal such asa wireless

LAN packet, or the like and may be embedded in the station 100 orprovided as an exterior. According to the embodiment, the transceiver120 may include at least one transmit/receive module using differentfrequency bands. For example, the transceiver 120 may includetransmit/receive modules having different frequency bands such as 2.4GHz, 5 GHz, and 60 GHz. According to an embodiment, the station 100 mayinclude a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the AP or an external station according to a wirelessLAN standard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 120 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of transmit/receive modules, each transmit/receive module maybe implemented by independent elements or a plurality of modules may beintegrated into one chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 controls various operations of radio signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality oftransmit/receive modules using different frequency bands. That is, theAP 200 according to the embodiment of the present invention may includetwo or more transmit/receive modules among different frequency bands,for example, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200may include a transmit/receive module using a frequency band of 6 GHz ormore and a transmit/receive module using a frequency band of 6 GHz orless. The respective transmit/receive modules may perform wirelesscommunication with the station according to a wireless LAN standard of afrequency band supported by the corresponding transmit/receive module.The transceiver 220 may operate only one transmit/receive module at atime or simultaneously operate multiple transmit/receive modulestogether according to the performance and requirements of the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 controls variousoperations such as radio signal transmission/reception of the AP 200according to the embodiment of the present invention. A detailedembodiment thereof will be described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

When data is transmitted using Orthogonal Frequency Division Modulation(OFDMA) or Multi Input Multi Output (MIMO), any one wirelesscommunication terminal may transmit data to a plurality of wirelesscommunication terminals simultaneously. Also, any one wirelesscommunication terminal may simultaneously receive data from a pluralityof wireless communication terminals. An embodiment of the presentinvention in which any one wireless communication terminal transmitsdata to a plurality of wireless communication terminals will bedescribed with reference to drawings after FIG. 6. Especially, a casewhere any one wireless communication terminal transmits information ondata transmission to a plurality of wireless communication terminalswill be described with reference to drawings after FIG. 6.

At this time, any one wireless communication terminals may allocate asub-channel to each of the plurality of wireless communicationterminals. The sub-channel is a sub-frequency band included in a channelhaving a minimum unit frequency bandwidth used by any one wirelesscommunication terminal. Also, the minimum unit frequency bandwidthindicates the size of the smallest frequency band used by the firstwireless communication terminal. In a specific embodiment, the minimumunit frequency bandwidth may be 20 MHz.

For convenience of description, any one wireless communication terminalthat communicates simultaneously with a plurality of wirelesscommunication terminals is referred to as a first wireless communicationterminal and a plurality of wireless communication terminals thatsimultaneously communicate with the first wireless communicationterminal are referred to as a plurality of second wireless communicationterminals. In addition, the first wireless communication terminal may bereferred to as a base wireless communication terminal. In addition, thefirst wireless communication terminal may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in communication with a plurality of wireless communicationterminals. Specifically, the first wireless communication terminal mayperform the role of a cell coordinator. At this time, the first wirelesscommunication terminal may be the access point 200. In addition, thesecond wireless communication terminal may be the station 100 associatedwith the access point 200. In a specific embodiment, the first wirelesscommunication terminal may be a wireless communication terminal thatallocates a communication medium resource and performs scheduling in anindependent network, such as an ad-hoc network, which is not connectedto an external distribution service. In addition, the first wirelesscommunication terminal may be at least one of a base station, an eNB,and a transmission point TP.

When the first wireless communication terminal transmits data to aplurality of second wireless communication terminals using OFDMA, thefirst wireless communication terminal allocates a sub-frequency band toeach of the plurality of second wireless communication terminals. Then,the first wireless communication terminal may transmit data through asub-frequency band allocated to each of the plurality of second wirelesscommunication terminals. Accordingly, the first wireless communicationterminal should notify the plurality of second wireless communicationterminals that data is to be transmitted first. Then, the secondwireless communication terminal should signal the sub-frequency bandallocated to each of the plurality of second wireless communicationterminals to the plurality of second wireless communication terminals.Specifically, the first wireless communication terminal may transmit aMAC frame including information on a plurality of second wirelesscommunication terminals that are to receive data to the plurality ofsecond wireless communication terminals. At this time, the informationon the plurality of second wireless communication terminals may includean identifier for identifying the plurality of second wirelesscommunication terminals that are to receive data. In addition, theinformation on the plurality of second wireless communication terminalsmay include information on a frequency band allocated to each of theplurality of second wireless communication terminals. The secondwireless communication terminal receives data through the allocatedfrequency band. Further, the second wireless communication terminal maytransmit a transmission completion frame indicating transmissioncompletion. Also, the second wireless communication terminal maytransmit data to the first wireless communication terminal through theallocated frequency band. According to a specific embodiment, a frameincluding information on a plurality of second wireless communicationterminals may serve as a role of the second wireless communicationterminal to trigger data transmission to the first wirelesscommunication terminal of the second wireless communication terminal.For convenience of description, a frame including information on aplurality of second wireless communication terminals is referred to as apoll frame.

The Poll frame will be described in detail with reference to FIGS. 6 to8.

FIG. 6 is a view illustrating a structure of a poll frame according toan embodiment of the present invention.

The poll frame may include a Basic Service Set Identifier (BSSID) foridentifying a basic service set in which the poll frame is transmitted.At this time, the BSSID may indicate the MAC address of the firstwireless communication terminal transmitting the poll frame.

The poll frame may include source address information indicating theaddress of the first wireless communication terminal transmitting thepoll frame. At this time, the address of the first wirelesscommunication terminal may be the MAC address of the first wirelesscommunication terminal. The BSSID and the source address information maybe identically used as information indicating the first wirelesscommunication terminal. Accordingly, according to a specific embodiment,the poll frame may include any one of the BSSID and the source addressinformation.

The poll frame may include length information indicating the length ofthe poll frame. The second wireless communication terminal may obtainthe number of the second wireless communication terminals participatingin the data transmission based on the length information. Specifically,the second wireless communication terminal obtains a variable length bysubtracting the length of the field of the fixed poll frame from thelength of the poll frame indicated by the length information regardlessof the number of the second wireless communication terminalsparticipating in the data transmission. Then, the second wirelesscommunication terminal may divide the obtained variable length by thelength of the variable field required for one second wirelesscommunication terminal, thereby obtaining the number of the secondwireless communication terminals participating in the data transmission.

The poll frame may include channel vector information indicatinginformation of a frequency channel allocated to the second wirelesscommunication terminal. The channel vector information may include afrequency channel allocated to the second wireless communicationterminal.

The poll frame may include information for identifying a plurality ofsecond wireless communication terminals that are to receive datatransmitted by the first wireless communication terminal. Specifically,the poll frame may include an identifier for identifying each of aplurality of second wireless communication terminals that are to receivedata transmitted by the first wireless communication terminal. At thistime, the identifier may be an Association Identifier (AID) foridentifying an association between the first wireless communicationterminal and the second wireless communication terminal.

The second wireless communication terminal may recognize the channelallocated to the second wireless communication terminal based on thechannel vector information and the information for identifying aplurality of second wireless communication, and receive data from thefirst wireless communication terminal through the corresponding channel.In addition, the second wireless communication terminal may recognizethe channel allocated to the second wireless communication terminalbased on the channel vector information, and transmit data to the firstwireless communication terminal through the corresponding channel. Aspecific format of channel vector information will be described laterwith reference to FIGS. 9 to 18.

In a specific embodiment, the poll frame may have the same structure asthat of the embodiment of FIG. 6. Specifically, the poll frame mayinclude a frame control field indicating the control information of aframe. The poll frame may include a BSSID field indicating a BSSID. Thepoll frame may include a source address (SA) field indicating sourceaddress information. The poll frame may include a length fieldindicating length information. The poll frame may include a CH vectorfield indicating channel vector information. The poll frame may includean STA ID field indicating the address of the second wirelesscommunication terminal that is to receive data transmitted by the firstwireless communication terminal. At this time, the STA ID field may belocated immediately before or immediately after the CH vector field.Specifically, the STA ID field may be located immediately before orimmediately after the CH vector field indicating the frequency bandallocated by the second wireless communication terminal indicated by theSTA ID field.

The poll frame may include an FCS field including a cyclical redundancycheck (CRC) value for error detection.

FIG. 7 is a view illustrating a structure of a poll frame according toanother embodiment of the present invention.

The poll frame may include duration information indicating a timerequired for data transmission after poll frame transmission. Throughthis, it is possible to prevent other wireless communication terminalsfrom accessing a frequency channel used for data transmission beforedata transmission is terminated.

In addition, the poll frame may include information indicating thenumber of second wireless communication terminals to which the pollframe allocates a frequency channel.

In a specific embodiment, the poll frame may have the same structure asthat of the embodiment of FIG. 7. Specifically, the poll frame mayinclude a duration field indicating duration information. Also,depending on a specific situation, the duration field may indicate thenumber of second wireless communication terminals to which the pollframe allocates a frequency channel. Also, depending on a specificsituation, the duration field may indicate length information of thepoll frame.

As described above, when a first wireless communication terminal and aplurality of second wireless communication terminals communicate usingthe OFDMA, it is necessary to signal the plurality of second wirelesscommunication terminals of channel information allocated to each of theplurality of second wireless communication terminals. For this, the pollframe may include channel vector information indicating information of afrequency channel allocated to the second wireless communicationterminal. Such channel vector information may be used to indicateinformation of a channel allocated to the second wireless communicationterminal even in a MAC frame other than a poll frame or the preamble ofa signal including a poll frame. At this time, a MAC frame other than apoll frame may be a data frame including data. Specifically, the headerof a physical frame may include channel vector information. In such acase, the second wireless communication terminal may decode the headerof a physical frame and obtain information on a frequency band allocatedto the second wireless communication terminal. Accordingly, the secondwireless communication terminal may quickly obtain information on afrequency band allocated to the second wireless communication terminal.

An embodiment in which the specific format of channel vector informationand the channel vector information are used will be described withreference to FIGS. 8 to 18.

FIG. 8 is a view illustrating a structure of a CH vector field in a pollframe according to an embodiment of the present invention.

As OFDMA transmission becomes possible, a plurality of second wirelesscommunication terminals according to an embodiment of the presentinvention may divide a frequency band having the minimum unit frequencybandwidth into a plurality of frequency bands. At this time, the minimumunit frequency bandwidth represents a minimum bandwidth used by thefirst wireless communication terminal. Then, each of the plurality ofsecond wireless communication terminals may communicate with the firstwireless communication terminal at the same time using each of theplurality of divided frequency bands. At this time, the minimum unitfrequency bandwidth may be 20 MHz. Therefore, the channel vectorinformation may include sub-channel information as well as channelinformation. At this time, the channel information is information on achannel having a bandwidth greater than the minimum unit frequencybandwidth. The sub-channel information, as a sub-band included in achannel, is information on a sub-channel having a bandwidth less thanthe minimum unit frequency bandwidth.

In a specific embodiment, a channel usage pattern available for thefirst wireless communication terminal and the second wirelesscommunication terminal may be predefined. In this case, a channel otherthan the predetermined channel usage pattern may not be used. At thistime, the channel usage pattern may indicate whether the range of afrequency band and the frequency band are combined. Such a channel usagepattern may be set for various regulations and technical feasibility.Also, such a channel usage pattern may be represented by an index.

Therefore, the channel vector information may include index informationindicating a channel usage pattern. Specifically, the channel vectorinformation may include channel index information. And the channelvector information may include sub-channel index information indicatinga sub-channel.

In addition, in order to prevent the size of a poll frame from becominglarge as the size of the channel vector information becomes too large,the channel vector information may include channel allocationinformation on a predetermined number of the second wirelesscommunication terminals. Specifically, when it is necessary to transmitchannel allocation information to second wireless communicationterminals of more than a predetermined number, the first wirelesscommunication terminal may divide channel allocation information for theplurality of second wireless communication terminals into a plurality ofpoll frames and transmit them.

In addition, in order to prevent the size of a poll frame from becominglarge as the size of the channel vector information becomes too large,the channel vector information may include channel information by asecond wireless communication terminal group unit including a pluralityof second wireless communication terminals instead of a second wirelesscommunication terminal unit. At this time, the group of the secondwireless communication terminals is a set including the plurality ofsecond wireless communication terminals. Specifically, the channelvector information may include a group identifier for identifying thegroup of second wireless communication terminals and channel informationallocated to the group of the second wireless communication terminal. Atthis time, the first wireless communication terminal may manage thegroup identifier. Specifically, the first wireless communicationterminal may allocate a group identifier to a plurality of secondwireless communication terminals in an association or a re-associationprocess. At this time, the first wireless communication terminal mayallocate a reserve group identifier remaining for future use to thesecond wireless communication terminal. In addition, the maximum numberof group identifiers that the first wireless communication terminalallocates may be limited to a predetermined number. When the channelvector information includes channel allocation information by each groupunit of the second wireless communication terminal, the first wirelesscommunication terminal may signal channel information allocated to eachsecond wireless communication terminal included in a group through thechannel vector information in the preamble of data.

In addition, when the same sub-channel is allocated to a plurality ofsecond wireless communication terminals, the poll frame may include agroup identifier for identifying the group of the second wirelesscommunication terminals instead of the identifier for identifying thesecond wireless communication terminal. Specifically, when MU-MIMO isused, a plurality of second wireless communication terminals may receiveone allocated sub-channel. In such a case, the poll frame may include agroup identifier for identifying the group of the second wirelesscommunication terminals instead of the identifier for identifying thesecond wireless communication terminal.

In a specific embodiment, the channel vector information includeschannel information allocated to the second wireless communicationterminal. At this time, the channel information may include channelindex information and sub-channel index information as described above.Specifically, the channel information may be a 2-byte field as in theembodiment of FIG. 8. In addition, the channel vector informationindicates channel index information through 12 bits and sub-channelindex information through 4 bits. When the first wireless communicationterminal uses a frequency band having a bandwidth larger than theminimum unit frequency bandwidth, a field indicating such sub-channelindex information may not be used. Specifically, when the minimum unitfrequency band is 20 MHz and the first wireless communication terminaluses a frequency band having a bandwidth greater than 20 MHz, the firstwireless communication terminal and the second wireless communicationterminal may not use the sub-channel index information. In addition,some of the 12 bits indicating the channel index information may be leftas reserved bits in preparation for the format change of the channelvector information.

As described above, the poll frame may include a duration fieldindicating duration information. Also, depending on a specificsituation, the duration field may indicate the number of second wirelesscommunication terminals to which the poll frame allocates a frequencychannel. Also, depending on a specific situation, the duration field maybe information indicating the number of second wireless communicationterminals to which the poll frame allocates a channel. At this time, thesecond wireless communication terminal may determine the length of thepoll frame based on the duration field. This is because the length ofthe poll frame becomes longer as the number of second wirelesscommunication terminals allocating a channel becomes larger.

Channel vector information is described with reference to FIG. 8. Amethod of displaying a channel index included in channel vectorinformation will be described in detail with reference to FIGS. 9 to 13.

FIG. 9 is a view illustrating a channel index of a 5 GHz frequency bandaccording to an embodiment of the present invention, and FIG. 10 is aview illustrating a channel index of a 5 GHz frequency band according toanother embodiment of the present invention.

When the first wireless communication terminal uses only a combinationof contiguous frequency bands, the same channel index as in theembodiment of FIG. 9 may be used. In such a case, the number ofcontiguous frequency channels is 256 or less. Therefore, a field forindicating the channel index information in the channel vectorinformation may be a field of 8 bits or less.

In a specific embodiment, the first wireless communication terminal andthe second wireless communication terminal may use a combination ofnon-contiguous frequency bands. In such a case, the same channel indexas in the embodiment of FIG. 10 may be used. For example, the channelindex 800 in FIG. 10(c) represents a frequency band combining thefrequency bands indicated by each of the channel index 4 and the channelindex 24, which are not contiguous to each other. At this time, thenumber of available channels may be 256 or more. In such a case, a fieldfor indicating the channel index information in the channel vectorinformation may be a field of 8 bits or more. Specifically, the sum ofthe size of a field indicating channel index information and the size ofa field indicating sub-channel index information may be 16 bits.Specifically, the field indicating the channel index information may bea 12-bit field. Also, the first wireless communication terminal and thesecond wireless communication terminal may use a bandwidth that is notone, two, four, or eight times the minimum unit frequency bandwidth. Forexample, in the embodiment of FIG. 10(b) in which a minimum unitfrequency bandwidth is 20MHz, the frequency band indicated by thechannel index 240 has a 100 MHz bandwidth that is five times the minimumunit frequency bandwidth of 20 MHz. Also, the first wirelesscommunication terminal and the second wireless communication terminalmay use frequency bands that is adjacent to but is not utilizedsimultaneously in 802.11ac. For example, the channel index 75 in FIG.10(a) represents a frequency band combining the frequency bandsindicated by each of the channel index 10 and the channel index 75.

As described above, the channel vector information may includesub-channel index information. At this time, the sub-channel indexinformation may indicate sub-channel or sub-carrier allocation.

In addition, the channel vector information including sub-channel indexinformation may be included in the poll frame as described above. Inanother specific embodiment, the channel vector information includingsub-channel index information may be included in the preamble of a frametransmitted from the first wireless communication terminal to the secondwireless communication terminal. At this time, the frame may be a dataframe including data. Such sub-channel index information will bedescribed with reference to FIGS. 11 to 18.

FIG. 11 is a view illustrating a sub-channel index in a frequency bandof 20 MHz according to an embodiment of the present invention.

In a specific embodiment, the first wireless communication terminal andthe second wireless communication terminal may divide a frequency bandhaving the minimum unit frequency bandwidth into eight sub-frequencybands. At this time, the first wireless communication terminal and thesecond wireless communication terminal may use a combination of eightsub-frequency bands as a sub-channel. The minimum unit frequencybandwidth may be 20 MHz. The first wireless communication terminal andthe second wireless communication terminal may use the fifteensub-channels as shown in FIG. 11 by combining eight sub-frequency bandswith adjacent sub-frequency bands. In addition, when the first wirelesscommunication terminal and the second wireless communication terminalindicate the channel vector information by using the group identifier,the sub-channel index should represent the case that the second wirelesscommunication terminal is included in the corresponding group but doesnot receive a sub-channel. Therefore, the number of cases that thesub-channel index should express is 16 in total. Therefore, thesub-channel index may be represented by a 4-bit field.

FIG. 12 is a view illustrating a sub-channel index in a frequency bandof 20 MHz according to another embodiment of the present invention.

In a specific embodiment, the first wireless communication terminal andthe second wireless communication terminal may divide a frequency bandhaving a minimum unit frequency bandwidth into nine sub-frequency bands.The minimum unit frequency bandwidth may be 20 MHz. The first wirelesscommunication terminal and the second wireless communication terminalmay use the fifteen sub-channels as shown in FIG. 12 by combining eightsub-frequency bands with adjacent sub-frequency bands except for thefifth sub-frequency band. Except when all the minimum unit frequencybands are used, if the case that channel vector information is indicatedusing a group identifier is included, the total number of sub-channelsis 15. In addition, the sub-channel index should cover the case that thesecond wireless communication terminal is included in the correspondinggroup but does not receive a sub-channel. Therefore, the number of casesthat the sub-channel index should display is 16 in total. Therefore, thesub-channel index may be represented by a 4-bit field.

FIG. 13 is a view illustrating a sub-channel index in a frequency bandof 20 MHz including a combination of non-contiguous sub-frequency bandsaccording to another embodiment of the present invention.

In a specific embodiment, the first wireless communication terminal andthe second wireless communication terminal may divide a frequency bandhaving a minimum unit frequency bandwidth into nine sub-frequency bands.The minimum unit frequency bandwidth may be 20 MHz. The first wirelesscommunication terminal and the second wireless communication terminalmay combine the nine sub-frequency bands without restriction and usethem as a sub-channel. Specifically, the first wireless communicationterminal and the second wireless communication terminal may combinenon-continuous sub-frequency bands and use them as one sub-channel. Forexample, as shown in FIG. 13, the sub-channel index 17 represents afrequency band obtained by combining frequency bands indicated by thesub-channel index 1, the sub-channel index 2, and the sub-channel index5. In such a case, since the number of cases that a sub-channel indexshould represent is 16 or more, the sub-channel index may be representedby a field of 5 bits or more.

The preamble of a signal transmitted from the first wirelesscommunication terminal to the second wireless communication terminal mayinclude information on a frequency band or a sub-carrier allocated tothe second wireless communication terminal. In a specific embodiment,the preamble of a signal transmitted from the first wirelesscommunication terminal to the second wireless communication terminal mayinclude sub-channel index information. Specifically, the header of aphysical frame including data transmitted from the first wirelesscommunication terminal to each of the plurality of second wirelesscommunication terminals may include information on a frequency band or asub-carrier allocated to each of the second wireless communicationterminals. For example, a physical frame including data transmitted fromthe first wireless communication terminal to each of the plurality ofsecond wireless communication terminals may include a signaling fieldfor signaling a signal including data transmitted by the physical frame.At this time, the signaling field may include information on a frequencyband or a sub-carrier allocated to each of the second wirelesscommunication terminals.

At this time, the signaling field is a field including information forsignaling data included in the physical frame. The signaling field maybe at least one of SIG-A for signaling information common to a pluralityof second wireless communication terminals, SIG-B for signalinginformation for each of the plurality of second wireless communicationterminals, and SIG-C for signaling other information. Through this, thesecond wireless communication terminal may decode the preamble signaltransmitted from the first wireless communication terminal and obtaininformation on a frequency band or a sub-carrier allocated to the secondwireless communication terminal. A specific format of information on theallocated frequency band or sub-carrier included in the preamble of asignal transmitted from the first wireless communication terminal to thesecond wireless communication terminal will be described with referenceto FIGS. 14 to 18.

FIG. 14 is a view illustrating a preamble including sub-channelinformation according to an embodiment of the present invention.

The channel vector information may include channel allocationinformation in a group unit of the second wireless communicationterminals instead of a second wireless communication terminal unit. Atthis time, the group of the second wireless communication terminals is aset including the plurality of second wireless communication terminals.In addition, the sub-channel information included in the preamble of asignal transmitted from the first wireless communication terminal to thesecond wireless communication terminal may include the group identifierof a group including the second wireless communication terminal to whichthe sub-channel is allocated.

In addition, the sub-channel information may include informationindicating a sub-channel allocated to the second wireless communicationterminal. At this time, the information indicating the sub-channel maybe a sub-channel index indicating the sub-channel.

In a specific embodiment, the format of the sub-channel informationincluded in the preamble may be one as shown in FIG. 14. Specifically,the sub-channel information may include a Group ID field indicating agroup identifier. In a specific embodiment, the Group ID field may be afield of 6 bits or more. For example, when the maximum number of secondwireless communication terminals connected to one first wirelesscommunication terminal is 4, the Group ID field may be a 6-bit field. Inaddition, when the maximum number of second wireless communicationterminals connected to one first wireless communication terminal is morethan 4, the Group ID field may be a field of more than 6 bits.

In addition, the sub-channel information may include a CH vector fieldindicating a sub-channel allocated to the second wireless communicationterminal. In a specific embodiment, the CH vector field may indicatethat no sub-channel is allocated to the second wireless communicationterminal corresponding to the CH vector field. In such a case, the valueof the CH vector field corresponding to the second wirelesscommunication terminal not participating in the transmission with thefirst wireless communication may be zero. In a specific embodiment, theCH vector field may be a 4-bit field. At present, Multi User-Multi Inputand Multi Output (MU-MIMO) allows the simultaneous connection of a totalof four wireless communication terminals to the first wirelesscommunication terminal. Thus, the sub-channel information may includefour CH vector fields. In addition, when the number of second wirelesscommunication terminals that simultaneously access the first wirelesscommunication terminal allowed by MU-MIMO is increased, the number ofthe CH vector fields may be increased

FIG. 15 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

In preparation for the case that the number of second wirelesscommunication terminals connected to one first wireless communicationterminal at the same time is increased, the number of CH vector fieldsmay not be limited as shown in FIG. 15.

In such a case, the signaling field including the information on thefrequency-band allocated to the second wireless communication terminalhas a variable length.

FIG. 16 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

As described with reference to FIG. 15, when the number of CH vectorfields is not limited, the second wireless communication terminal has tocontinuously decode a variable signal without knowing the number of CHvector fields. To solve this problem, the sub-channel information of thepreamble included in a signal transmitted from the first wirelesscommunication terminal to the second wireless communication terminal mayinclude information indicating the number of the second wirelesscommunication terminals to which the sub-channel is allocated. Inanother specific embodiment, if one second wireless communicationterminal is allocated per one sub-channel, the sub-channel informationmay include the number of allocated sub-channels.

In a specific embodiment, the sub-channel information may include aNumber of User field indicating the number of second wirelesscommunication terminals to which a sub-channel is allocated, as in theembodiment of FIG. 16. At this time, the Number of User field may be a4-bit field.

In another specific embodiment, the sub-channel information may includea channel divide factor field indicating the number of sub-channelsallocated to the plurality of second wireless communication terminals,as in the embodiment of FIG. 16. At this time, the Channel divide factorfield may be a 4-bit field.

Through such an embodiment, the second wireless communication terminalmay accurately recognize the size of a preamble to be decoded.

FIG. 17 is a view illustrating a preamble including sub-channelinformation according to another embodiment of the present invention.

According to the above-described embodiment, even if a sub-channel isnot allocated, the second wireless communication terminal should decodeall the sub-channel information to determine whether the sub-channel isallocated. In order to prevent this, the sub-channel informationincluded in the preamble of a signal transmitted from the first wirelesscommunication terminal to the second wireless communication terminal mayinclude information indicating whether the OFDMA communication using thesub-channel is used or not.

In a specific embodiment, the sub-channel information may include anOFDMA Indication field indicating whether to use OFDMA communicationusing a sub-channel, as in the embodiment of FIG. 17. In a specificembodiment, the OFDMA Indication field may be a 1-bit flag. For example,if the value of the OFDMA Indication field is 1, the OFDMA Indicationfield may indicate that the first wireless communication terminalallocates a sub-channel to the second wireless communication terminalfor OFDMA communication using the sub-channel.

When the OFDMA Indication field is a 1-bit flag, the Number of Userfield described above may be a 3-bit field. Also, if the value indicatedby the Number of User field is N, it may indicate that a sub-channel isallocated to the N-2 second wireless communication terminal. The reasonwhy the sub-channel is allocated to the N-2 second wirelesscommunication terminals instead of the N second wireless communicationterminals is that the sub channel is allocated to two or more secondwireless communication terminals when OFDMA communication using thesub-channel is used.

FIG. 18 is a view illustrating a CH vector field indicating acombination of non-contiguous sub-band channels according to anotherembodiment of the present invention.

In the above-described specific embodiment, it is described that the CHvector field included in the sub-channel information may be 4 bits.However, when a sub-channel indicating a combination of non-contiguoussub-bands is supported, the number of sub-channels is increased, so thatthe CH vector field may be a field of 5 bits or more.

With reference to FIGS. 19 to 24, a method of transmitting a controlframe when the first wireless communication terminal transmits data to aplurality of second wireless communication terminals will be described.

FIG. 19 is a view illustrating that an access point transmits data to aplurality of stations using a poll frame.

The first wireless communication terminal may set a network allocationvector (NAV) through various embodiments. Specifically, the firstwireless communication terminal may transmit a transmission notificationframe for notifying data transmission to a plurality of second wirelesscommunication terminals that are to transmit data. At this time, each ofthe plurality of second wireless communication terminals may transmit areception ready frame indicating that each second wireless communicationterminal is ready to receive data. In a specific embodiment, thetransmission notification frame may be a Request to Send (RTS) frame. Inaddition, the reception ready frame may be a Clear to Send (CTS) frame.In yet another specific embodiment, the setting of the NAV may beomitted.

The first wireless communication terminal transmits the above-describedpoll frame to the plurality of second wireless communication terminals.Specifically, the first wireless communication terminal may transmit thepoll frame to the plurality of second wireless communication terminalsthrough the primary channel of a frequency band used by the firstwireless communication terminal. At this time, the primary channelrepresents a channel having a minimum unit frequency bandwidth from theminimum frequency value of a frequency band used by the first wirelesscommunication terminal. Also, a secondary channel represents a channelother than the primary channel. In another specific embodiment, thefirst wireless communication terminal may transmit the poll framethrough a secondary channel as well as a primary channel. When the firstwireless communication terminal transmits the poll frame only through aprimary channel, a wireless communication terminal belonging to a BSSdifferent from that of the first wireless communication terminal mayaccess a secondary channel. As described above, when the first wirelesscommunication terminal transmits the poll frame through the primarychannel in addition to the secondary channel, it is possible to preventa wireless communication terminal belonging to another BSS fromaccessing the secondary channel.

Each of the plurality of second wireless communication terminalsreceives a poll frame.

Each of the plurality of second wireless communication terminals maydetermine whether the first wireless communication terminal transmitsdata to each of the plurality of second wireless communication terminalsbased on the poll frame. Specifically, when the poll frame includes anidentifier indicating the second wireless communication terminal, thesecond wireless communication terminal may determine that the firstwireless communication terminal transmits data to the second wirelesscommunication terminal.

Further, each of the plurality of second wireless communicationterminals may obtain information on a frequency band allocated to eachof the plurality of second wireless communication terminals based on thepoll frame. Specifically, each of the plurality of second wirelesscommunication terminals may obtain the above-described channel vectorinformation from the poll frame. For example, each of the plurality ofsecond wireless communication terminals may obtain information on achannel allocated to the second wireless communication terminal andinformation on a sub-channel from the poll frame.

The first wireless communication terminal transmits data to each of theplurality of second wireless communication terminals through a frequencyband allocated to each of the plurality of second wireless communicationterminals.

Each of the plurality of second wireless communication terminals thatreceive the data may transmit a transmission completion frame indicatingtransmission completion to the first wireless communication terminalthrough various embodiments. Specifically, each of the plurality ofsecond wireless communication terminals may transmit a transmissioncompletion frame to the first wireless communication terminal through afrequency band allocated to each of the plurality of second wirelesscommunication terminals. In addition, the transmission completion framemay be an ACK frame.

In the embodiment of FIG. 19, the access point AP and the first stationSTA1 to the seventh station STA7 set the NAV for data transmissionthrough various methods. At this time, the access point AP and the firststation STA1 to the seventh station STA7 may set the NAV through the RTSframe and the CTS frame.

The access point AP transmits a poll frame through a primary channelhaving a bandwidth of 20 MHz. As described above, the poll frameincludes information on a frequency band allocated to each of the firststation STA1 to the seventh stations STA7.

Each of the first station STA1 to the seventh stations STA7 receives thepoll frame and obtains information on the frequency band allocated toeach of the first station STA1 to the seventh stations STA7.

The access point AP transmits data to the first station STA1 to theseventh station STA7 through the frequency band allocated to each of thefirst station STA1 to the seventh station STA7. Specifically, the accesspoint AP transmits data to the first station STA1 through the firstsub-channel Sub-channel #1 of the primary channel. In addition, theaccess point AP transmits data to the second station STA2 through thesecond sub-channel Sub-channel #2 of the primary channel. In addition,the access point AP transmits data to the third station STA3 through thethird sub-channel Sub-channel #3 and the fourth sub-channel Sub-channel#4 of the primary channel. In addition, the access point AP transmitsdata to the fourth station STA4 through the first sub-channelSub-channel #1 of the secondary channel. In addition, the access pointAP transmits data to the fifth station STA5 through the secondsub-channel Sub-channel #2 of the secondary channel. In addition, theaccess point AP transmits data to the sixth station STA6 through thethird sub-channel Sub-channel #3 of the secondary channel. In addition,the access point AP transmits data to the seventh station STA7 throughthe fourth sub-channel Sub-channel #4 of the secondary channel.

Each of the first station STA1 to the seventh station STA7 receives datathrough a frequency band allocated to each of the first station STA1 tothe seventh station STA7.

Each of the first station STA1 to the seventh station STA7 may transmitthe ACK frame to the first wireless communication terminal throughvarious embodiments.

However, in such an embodiment, when the RTS frame does not signal thesecond wireless communication terminal that is to receive data, thesecond wireless communication terminal knows that the first wirelesscommunication terminal transmits the data after receiving the pollframe. Therefore, the first wireless communication terminal may notreceive the CTS frame from the second wireless communication terminalbefore the poll frame transmission. To solve this, a modified RTS frameis needed. This will be described later with reference to FIG. 22.

FIG. 20 is a view illustrating that an access point transmits anRTS-to-Self frame and transmits data to a plurality of stations aftertransmitting a poll frame.

The first wireless communication terminal may transmit a frame fornotifying the first wireless communication terminal is to transmit datato the plurality of second wireless communication terminals. The framefor notifying that the first wireless communication terminal is totransmit data to the plurality of second wireless communicationterminals may be an RTS-to-Self frame. The RTS-to-Self frame representsan RTS frame of which receiver address is a wireless communicationterminal that transmits a frame. The format of a specific frame otherthan the receiver address may be the same as the format of the RTS framedefined by the 802.11 standard.

The first wireless communication terminal may transmit the RTS-to-Selfframe to the plurality of second wireless communication terminalsthrough the frequency band having a bandwidth equal to or greater thanthe minimum unit bandwidth. Specifically, the first wirelesscommunication terminal may transmit the RTS-to-Self frame to theplurality of second wireless communication terminals through thefrequency band having the minimum unit bandwidth. At this time, theminimum unit bandwidth may be 20 MHz as described above. Through this,the first wireless communication terminal allows a wirelesscommunication terminal, which is not able to detect a frequency bandless than the minimum unit bandwidth, to set the NAV.

In a specific embodiment, the first wireless communication terminal maytransmit the RTS-to-Self frame to the plurality of second wirelesscommunication terminals through the primary channel of a frequency bandused by the first wireless communication terminal. In another specificembodiment, the first wireless communication terminal may transmit theRTS-to-Self frame through a secondary channel as well as a primarychannel. When the first wireless communication terminal transmits theRTS-to-Self frame only through a primary channel, a wirelesscommunication terminal belonging to a BSS different from that of thefirst wireless communication terminal may access a secondary channel. Asdescribed above, when the first wireless communication terminaltransmits the RTS-to-Self frame through the primary channel in additionto the secondary channel, it is possible to prevent a wirelesscommunication terminal belonging to another BSS from accessing thesecondary channel.

Also, the first wireless communication terminal may transmit theabove-described poll frame to the plurality of second wirelesscommunication terminals when a predetermined time elapses after thetransmitting of the RTS-to-Self frame. At this time, the predeterminedtime may be a Short Inter-Frame Space (SIFS) defined in the 802.11standard.

As described above, each of the plurality of second wirelesscommunication terminals may determine whether the first wirelesscommunication terminal transmits data to each of the plurality of secondwireless communication terminals based on the poll frame. Further, eachof the plurality of second wireless communication terminals may obtaininformation on a frequency band allocated to each of the plurality ofsecond wireless communication terminals based on the poll frame.

Each of the plurality of second wireless communication terminals thatreceive the poll frame transmits a response frame for the poll frame tothe first wireless communication terminal after a predetermined timefrom the poll frame transmission time. At this time, the predeterminedtime may be SIFS defined in the 802.11 standard. If a time for thesecond wireless communication terminal to process the poll frame isinsufficient, the predetermined time may be the Point CoordinateInter-Frame Space (PIFS) defined by the 802.11 standard or longer.

In the embodiment of FIG. 20, the first wireless communication terminaltransmits the RTS-to-Self frame when a channel is idle for apredetermined time or longer. At this point, the predetermined time maybe Distributed Inter-Frame Space (DIFS) defined in 802.11. Specifically,the first wireless communication terminal transmits an RTS-to-Self framein each minimum frequency bandwidth. At this time, the minimum unitfrequency bandwidth is 20 MHz.

The first wireless communication terminal transmits the poll frame tothe plurality of second wireless communication terminals. Specifically,after SIFS from when the RTS-to-Self frame is transmitted, the firstwireless communication terminal transmits a poll frame to the pluralityof second wireless communication terminals. At this time, the firstwireless communication terminal may transmit the poll frame to theplurality of second wireless communication terminals through the primarychannel.

Each of the plurality of second wireless communication terminals maytransmit a CTS frame to the first wireless communication terminalthrough various embodiments. Then, the operations of the first wirelesscommunication terminal and the second wireless communication terminalmay be the same as those of the embodiment of FIG. 19.

FIG. 21 is a view illustrating that an access point transmits a pollframe before transmitting an RTS frame and a CTS frame and transmitsdata to a plurality of stations.

The first wireless communication terminal may transmit the poll frame tothe plurality of second wireless communication terminals before settingthe NAV. Specifically, the first wireless communication terminal maytransmit the poll frame before transmitting the RTS frame to theplurality of second wireless communication terminals. Through this, thefirst wireless communication terminal may quickly signal information onthe plurality of second wireless communication terminals that are toreceive data to the plurality of second wireless communicationterminals. At this time, the information on the plurality of secondwireless communication terminals that are to receive data may beinformation for identifying the plurality of second wirelesscommunication terminals that are to receive data. Specifically, theinformation for identifying the plurality of second wirelesscommunication terminals may be an identifier for identifying each of theplurality of second wireless communication terminals. In addition, theinformation on the plurality of second wireless communication terminalsthat are to receive data may be information on a frequency bandallocated to each of the plurality of second wireless communicationterminals. The information on the frequency band allocated to each ofthe plurality of second wireless communication terminals may include atleast one of information on a channel and information on a sub-channel.

After the first wireless communication terminal transmits a poll frame,the first wireless communication terminal and the second wirelesscommunication terminal may set the NAV through various embodiments.Specifically, the first wireless communication terminal and the secondwireless communication terminal may set the NAV through the RTS frameand the CTS frame.

In the embodiment of FIG. 21, when the frequency band is idle for apredetermined time or longer, the access point AP transmits a poll frameto the first station STA1 to the seventh station STA7. At this time, thepredetermined time may be DIFS defined in 802.11.

The access point AP transmits a poll frame through a primary channelhaving a minimum unit frequency bandwidth. At this time, the minimumunit frequency bandwidth is 20 MHz.

The access point AP and the first station STA1 to the fourth stationSTA7 set the NAV through various embodiments. Specifically, the accesspoint AP and the first station STA1 to the fourth station STA7 set theNAV through the RTS frame and the CTS frame.

Then, operations of the access point AP and the first station STA1 tothe seventh station STA7 may be the same as those of the embodiment ofFIG. 19 described above.

The embodiments described with reference to FIGS. 19 to 21 may be basedon setting a NAV through transmission of an legacy RTS frame and CTSframe. When a new type RTS frame is used, data transmission using OFDMAis signaled to a plurality of second wireless communication terminalswithout transmission of a poll frame. This will be described withreference to FIG. 22.

FIG. 22 is a view illustrating that an access point transmits data to aplurality of stations using an M-RTS frame.

The first wireless communication terminal may transmit a frame forsimultaneously notifying the plurality of second wireless communicationterminals that it is ready to transmit data. At this time, the frame forsimultaneously notifying the plurality of second wireless communicationterminals that it is ready to transmit data may be referred to asMultiple-RTS (M-RTS).

Specifically, the M-RTS frame may include information on a plurality ofsecond wireless communication terminals to which the first wirelesscommunication terminal transmits data. The information on the pluralityof second wireless communication terminals may include an identifier foridentifying each of the plurality of second wireless communicationterminals. In addition, the information on the plurality of secondwireless communication terminals may include information on a frequencyband allocated to each of the plurality of second wireless communicationterminals. The information on the frequency band may include at leastone of information on a primary channel and information on asub-channel. When the information on the plurality of second wirelesscommunication terminals does not include information on the frequencyband allocated to each of the plurality of second wireless communicationterminals, the preamble of a signal including a data frame or an M-RTSframe, each of which is transmitted by the first wireless communicationterminal to the second wireless communication terminal, may includeinformation on a frequency band allocated to each of the plurality ofsecond wireless communication terminals.

Also, the first wireless communication terminal may transmit the M-RTSframe to the plurality of second wireless communication terminalsthrough the primary channel having the minimum unit bandwidth. In such acase, the plurality of second wireless communication terminals maydecode another channel as necessary while decoding the primary channel.Therefore, the operation efficiency of the second wireless communicationterminal may be increased.

In another specific embodiment, the first wireless communicationterminal may transmit an M-RTS frame for each channel having a minimumunit bandwidth. In such a case, the M-RTS frame may include onlyinformation on the second wireless communication terminal that receivesa corresponding allocated channel. For example, if the maximum number ofsecond wireless communication terminals capable of receiving datathrough a channel having a minimum unit bandwidth is four, the M-RTSframe may include information on up to four second wirelesscommunication terminals.

In another specific embodiment, the first wireless communicationterminal may transmit an M-RTS frame to each of the plurality of secondwireless communication terminals through a frequency band allocated tothe plurality of second wireless communication terminals. At this time,if the bandwidth of a frequency band allocated to the plurality ofsecond wireless communication terminals is the minimum unit frequencybandwidth, it is possible to transmit an legacy RTS frame. If thebandwidth of the frequency band allocated to the plurality of secondwireless communication terminals is smaller than the minimum unitfrequency bandwidth, the first wireless communication terminal maytransmit an M-RTS frame.

In the embodiment of FIG. 22, the access point AP transmits an M-RTSframe to each of the first station STA1 to the seventh station STA7 whenthe frequency band is idle for a predetermined time. At this time, thepredetermined time may be DIFS defined in the 802.11 standard.

Specifically, the access point AP transmits an M-RTS frame to each ofthe first station STA1 to the seventh station STA7 through a channelallocated to each of the first station STA1 to the seventh station STA7.At this time, since a sub-channel having a bandwidth of 5 MHz isallocated to each of the first station STA1 to the seventh station STA7,the access point AP transmits an M-RTS frame to each of the firststation STA1 to the seventh station STA7 through the sub-channel havinga bandwidth of 5 MHz.

Each of the first station STA1 to the seventh station STA7 may transmita CTS frame to the access point AP through various embodiments.

Then, operations of the access point AP and the first station STA1 tothe seventh station STAT may be the same as those of the embodiments ofFIGS. 19 to 21 described above.

Through such an embodiment, the first wireless communication terminalmay reduce the time for transmitting a control frame in order to signalthe plurality of second wireless communication terminals and set a NAV,as compared with the above-described embodiment.

However, since the M-RTS frame has a format different from that of thelegacy RTS frame, there is an issue that the NAV of a wirelesscommunication terminal that does not support the embodiment of thepresent invention may not be set.

As described above, the first wireless communication terminal may signalthe frequency band allocated to the plurality of second wirelesscommunication terminals through the preamble of a wireless communicationsignal. The structure of a physical frame and the concrete format of asignaling field for the above included in the physical frame will bedescribed in detail with reference to FIGS. 23 and 24.

FIG. 23 is a view illustrating a physical frame according to anembodiment of the present invention.

The signaling field included in the physical frame may includeinformation on a frequency band allocated to each of the plurality ofsecond wireless communication terminals. The information on thefrequency band allocated to each of the plurality of second wirelesscommunication terminals may include the above-described channel vectorinformation.

In addition, the signaling field may include information on a frequencyband allocated to each of the plurality of second wireless communicationterminals for each of the plurality of second wireless communicationterminals. Specifically, the signaling field may include a plurality offields, and each of the plurality of fields may indicate a set ofinformation on a frequency band allocated to each of the plurality ofsecond wireless communication terminals. Through this, the signalingfield decoding efficiency of the second wireless communication terminalmay be improved. Specifically, the second wireless communicationterminal may decode a field indicating a set of information on afrequency band allocated to the second wireless communication terminal,and may not decode a field located after the field indicating the secondwireless communication terminal.

In a specific embodiment, the signaling field includes a SIG-A fieldincluding information commonly applied to the plurality of secondwireless communication terminals and a SIG-B field including informationon each of the plurality of second wireless communication terminals. Atthis time, the SIG-B field may include information on the frequency-bandallocated to each of the plurality of second wireless communicationterminals.

Also, such a physical frame may be a data frame including datatransmitted by the first wireless communication terminal to each of theplurality of second wireless communication terminals, as describedabove.

In addition, the physical frame may include a training signal for eachsub-channel allocated to the plurality of second wireless communicationterminals. The training signal is a signal that assists the demodulationand decoding setting of a wireless communication terminal for receivingthe signal to be transmitted after the transmission of the trainingsignal. Specifically, the physical frame may include a short trainingsignal and a long training signal for each sub-channel allocated to theplurality of second wireless communication terminals.

A wireless communication terminal supporting an embodiment of thepresent invention may perform Automatic Gain Control (AGC) on an OFDMsymbol including data in a long training signal and a payload based on ashort training signal. In addition, a wireless communication terminalsupporting an embodiment of the present invention may performsynchronization with respect to the timing and frequency of an OFDMsymbol including data in a long training signal and a payload, based ona short training signal.

A wireless communication terminal supporting an embodiment of thepresent invention may estimate the fine frequency offset and the channelof an OFDM symbol including data included in the payload of a longtraining signal.

In the embodiment of FIG. 23, the physical frame includes an L-STFfield, an L-LTF field, an L-SIG field, an HE-SIG-A field, an HE-STFfield, an HE-LTF field, and an HE-SIG-B field.

The L-STF field indicates a short training signal decoded by both awireless communication terminal supporting the embodiment of the presentinvention and a wireless communication terminal not supporting theembodiment of the present invention. The short training signal is atraining signal having a relatively short signal length. Specifically, awireless communication terminal may perform Automatic Gain Control (AGC)on an OFDM symbol including an L-LTF field and an L-SIG field based on ashort training signal, and synchronize a timing and a frequency with theOFDM symbol including the L-SIG field.

The L-LTF field indicates a long training signal decoded by both awireless communication terminal supporting the embodiment of the presentinvention and a wireless communication terminal not supporting theembodiment of the present invention. The long training signal is atraining signal having a relatively long signal length. Specifically,the wireless communication terminal may estimate the fine frequencyoffset and the channel of the OFDM symbol including the L-SIG fieldbased on the long training signal.

The L-SIG field is signaling information decoded by both a wirelesscommunication terminal supporting the embodiment of the presentinvention and a wireless communication terminal not supporting theembodiment of the present invention. Specifically, the L-SIG fieldindicates information on a data rate and a data length.

The HE-SIG-A field indicates information that is commonly applied to aplurality of second wireless communication terminals. Specifically, theHE-SIG-A field may be the above-described SIG-A field.

The HE-STF field indicates a short training signal that the wirelesscommunication terminal supporting the embodiment of the presentinvention decodes. A wireless communication terminal supporting anembodiment of the present invention may perform Automatic Gain Control(AGC) on an OFDM symbol included in the HE-LTF field, the HE-SIG-Bfield, and the payload based on a short training signal. In addition, awireless communication terminal supporting an embodiment of the presentinvention may perform synchronization on the timing and frequency of anOFDM symbol included in the HE-LTF field, the HE-SIG-B field, and thepayload based on a short training signal.

The HE-LTF field indicates a long training signal that the wirelesscommunication terminal supporting the embodiment of the presentinvention decodes. A wireless communication terminal supporting anembodiment of the present invention may estimate the fine frequencyoffset and channel of an OFDM symbol included in the HE-LTF field, theHE-SIG-B field, and the payload based on a long training signal.

The HE-SIG-B field indicates information on a plurality of secondwireless communication terminals. Specifically, the HE-SIG-B field maybe the above-described SIG-B field.

The PSDU indicates the payload included in the physical frame.

FIG. 24 is a view illustrating a signaling field in a physical frameaccording to an embodiment of the present invention.

As described above, the signaling field included in the physical framemay include information on a frequency band allocated to each of theplurality of second wireless communication terminals. Specifically, thesignaling field may include bandwidth information indicating a bandwidthof a frequency band allocated to the second wireless communicationterminal. In addition, the signaling field may include STBC informationindicating whether space-time block coding (STBC) is applied to dataincluded in the payload. In addition, the signaling field may includesecond wireless communication terminal identifier information foridentifying a second wireless communication terminal corresponding toinformation signaled by the signaling field. When the same frequencyband is allocated to a plurality of second wireless communicationterminals, the signaling field may include group identifier informationfor identifying a group including a second wireless communicationterminal corresponding to information signaled by the signaling field.Also, the signaling field may include stream number informationindicating a space-time stream number transmitted through a frequencyband allocated to the second wireless communication terminal. Inaddition, the signaling field may include convolution coding informationindicating whether convolution coding is applied to data transmitted tothe second wireless communication terminal. Further, the signaling fieldmay include extra symbol information indicating whether or not an extraOFDM symbol is required by applying an LDPC coding to a signal includingdata to be transmitted to the second wireless communication terminal.The signaling field may include Modulation and Coding Scheme (MCS)information indicating an MCS of a signal including data transmitted tothe second wireless communication terminal.

Also, the signaling field may include a plurality of fields. At thistime, each of the plurality of fields may represent a set of informationon a frequency band allocated to each of the plurality of secondwireless communication terminals. Specifically, the signaling field mayinclude a first field indicating a set of information on a frequencyband allocated to any one second wireless communication terminal, and asecond field indicating a set of information on a frequency bandallocated to another second wireless communication terminal after thefirst field. At this time, each of the first field and the second fieldmay include at least one of the bandwidth information, the STBCinformation, the second wireless communication terminal identifierinformation, the group identifier information, the stream numberinformation, the convolution coding information, the extra symbolinformation, and the MCS information. Any one of the second wirelesscommunication terminals may decode the first field and may not decodethe second field.

In the embodiment of FIG. 24, the signaling field may include aBandwidth field, an STBC field, a Group ID field, a Number of space-timestreams field, a Coding field, an LDPC extra symbol field, and an MCSfield.

The Bandwidth field indicates the bandwidth of a frequency bandallocated to the second wireless communication terminal.

The STBC field indicates whether STBC is applied to data transmitted tothe second wireless communication terminal.

The Group ID field identifies a group including a second wirelesscommunication terminal that is to receive data transmitted through thecorresponding frequency band. In the case of the embodiment of FIG. 24,any one of the above-described sub-frequency bands is allocated to aplurality of second wireless communication terminals. Therefore, thesignaling field includes a Group ID field for identifying a group of thesecond wireless communication terminal instead of the field foridentifying the second wireless communication terminal.

The Number of space-time streams field indicates the number ofspace-time streams transmitted through the frequency band allocated tothe second wireless communication terminal.

The Coding field indicates whether convolution coding is applied to asignal including data to be transmitted to the second wirelesscommunication terminal.

The LDPC extra symbol field indicates whether an extra OFDM symbol isrequired by applying LDPC coding to a signal including data to betransmitted to the second wireless communication terminal.

The MCS field indicates an MCS of a signal including data correspondingto the second wireless communication terminal.

As described above, the specific signaling field of the embodiment ofFIG. 24 exists for each second wireless communication terminal.

FIG. 25 is a ladder diagram illustrating operations of a first wirelesscommunication terminal and a second wireless communication terminalaccording to an embodiment of the present invention.

The first wireless communication terminal 400 transmits a frameincluding information on the plurality of second wireless communicationterminals 500 to each of the plurality of second wireless communicationterminals 500 (S2501). Specifically, the information on the plurality ofsecond wireless communication terminals 500 may include information foridentifying the plurality of second wireless communication terminals500. Specifically, the information on the plurality of second wirelesscommunication terminals 500 may be information for identifying each ofthe plurality of second wireless communication terminals 500. Inaddition, the information on the plurality of second wirelesscommunication terminals 500 may be information identifying the group ofthe second wireless communication terminals.

In addition, the information on the plurality of second wirelesscommunication terminals 500 may include information on a frequency bandallocated to each of the plurality of second wireless communicationterminals 500. The information on the plurality of second wirelesscommunication terminals 500 may include the channel vector informationdescribed above. The channel vector information may include a channelindex indicating a channel including a frequency band allocated to thesecond wireless communication terminal 500 and a sub-channel indexindicating a sub-channel including a frequency band allocated to thesecond wireless communication terminal 500. At this time, thesub-channel is the sub-frequency band of a channel.

Specifically, the frame including information on the second wirelesscommunication terminal 500 may be the above-described poll frame. Inanother specific embodiment, the frame including information on thesecond wireless communication terminal 500 may be an M-RTS frame.

The first wireless communication terminal 400 may transmit a frame forsetting a NAV to each of the plurality of second wireless communicationterminals 500 before transmitting a frame including information on theplurality of second wireless communication terminals 500. In anotherspecific embodiment, the first wireless communication terminal 400 maytransmit a frame for setting a NAV to each of the plurality of secondwireless communication terminals 500 after transmitting a frameincluding information on the plurality of second wireless communicationterminals 500. At this time, the frame for setting the NAV may be an RTSframe. In addition, when transmitting a frame for setting a NAV througha channel smaller than the minimum unit frequency bandwidth, the firstwireless communication terminal 500 may transmit the above-describedRTS-to-Self frame through a frequency band greater than the minimum unitfrequency bandwidth.

The second wireless communication terminal 500 obtains information onthe plurality of second wireless communication terminals 500 from thereceived frame (S2503). Through this, the second wireless communicationterminal 500 may know to which of the second wireless communicationterminals 500 the first wireless communication terminal 400 is totransmit data. Also, according to a specific embodiment, the secondwireless communication terminal 500 may obtain information on thefrequency band allocated to the second wireless communication terminal500. Through this, the second wireless communication terminal 500 mayreceive data through the allocated frequency band. In addition, thesecond wireless communication terminal 500 may transmit a transmissioncompletion frame indicating data completion to the first wirelesscommunication terminal 400 through the allocated frequency band. At thistime, the transmission completion frame may be an ACK frame.

The first wireless communication terminal 400 transmits data to each ofthe plurality of second wireless communication terminals 500 (S2505).The second wireless communication terminal 500 receives data from thefirst wireless communication terminal 400 based on the obtainedinformation on the plurality of second wireless communication terminals500.

The physical frame including data may include a signaling field forsignaling a signal including data. In a specific embodiment, thesignaling field may include information on a frequency band allocated tothe second wireless communication terminal 500.

The information on the allocated frequency band may include the channelvector information described above. At this time, the channel vectorinformation may include a channel index indicating a channel including afrequency band allocated to the second wireless communication terminal500 and a sub-channel including the frequency band. At this time, thesub-channel is the sub-frequency band of a channel.

In addition, the information on the allocated frequency band may includeat least one of information on the bandwidth of the frequency bandallocated to the second wireless communication terminal 500 andModulation & Coding Scheme (MCS) information indicating MCS of a signalincluding data to be transmitted to the second wireless communicationterminal 500. In addition, the information on the allocated frequencyband may include at least one of group identifier information foridentifying a group of the second wireless communication terminals 500including the second wireless communication terminal 500 correspondingto information signaled by the signaling field and stream numberinformation indicating a space-time stream number transmitted throughthe frequency band allocated to the second wireless communicationterminal 500. In addition, the information on the allocated frequencyband may include at least one of space-time block coding (STBC)information indicating whether STBC is applied to a signal includingdata received by the second wireless communication terminal 500,convolution coding information indicating whether convolution coding isapplied to a signal including data received by the second wirelesscommunication terminal 500, and extra symbol information indicatingwhether an extra OFDM symbol is required by applying low-densityparity-check code (LDPC) coding is applied to a signal including datareceived by the second wireless communication terminal 500.

The signaling field may include information on the allocated frequencyband for each second wireless communication terminal 500. In a specificembodiment, the signaling field may include a plurality of fields, andeach of the plurality of fields may include a plurality of fieldsindicating a set of information on a frequency band allocated to each ofthe plurality of second wireless communication terminals 500. Throughthis, the second wireless communication terminal 500 may decode thefield indicating a set of information on a frequency band allocated tothe second wireless communication terminal 500, and stop decoding theplurality of fields.

In addition, the signaling field includes a SIG-A field includinginformation commonly applied to the plurality of second wirelesscommunication terminals 500 and a SIG-B field including information oneach of the plurality of second wireless communication terminals 500. Atthis time, the SIG-B field may include information on the frequency-bandallocated to each of the plurality of second wireless communicationterminals.

In a specific embodiment, the signaling field may follow the embodimentsdescribing the signaling field described with reference to FIGS. 6 to24.

In addition, the second wireless communication terminal 500 thatreceives data may transmit a transmission completion frame to the firstwireless communication terminal 400 through various embodiments.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the spirit and scope of the present invention.For example, each component specifically shown in the embodiments may bemodified and implemented. It should be interpreted that differencesrelating to such modifications and application are included in the scopeof the present invention defined in the appended claims.

1-20. (canceled)
 21. A base wireless communication terminal comprising:a transceiver; and a processor, wherein the processor is configured totransmit, by using the transceiver, a Multiple-Request to Send (M-RTS)frame to a plurality of wireless communication terminals, wherein theM-RTS frame is a medium access control (MAC) frame and includes aplurality of channel vector fields, wherein each of the plurality ofchannel vector fields indicates information on an allocatedsub-frequency band which is allocated to a wireless communicationterminal corresponding to each of the plurality of channel vector fieldsamong the plurality of wireless communication terminals, wherein theallocated sub-frequency band is allocated for communication between thebase wireless communication terminal and at least one of the pluralityof wireless communication terminals after a transmission of the M-RTSframe, and receive a Clear to Send (CTS) frame which is a response tothe M-RTS frame from the at least one of the plurality of wirelesscommunication terminals, wherein bits of each of the plurality ofchannel vector fields are divided into a first one or more bitsindicating a location of a channel, among a plurality of channels, whichincludes the allocated sub-frequency band, and a second one or more bitsindicating a location and a size of a sub-channel corresponding to theallocated sub-frequency band within the channel, wherein a number of thesecond one or more bits is larger than a number of the first one or morebits, wherein the sub-channel is included in the channel.
 22. The basewireless communication terminal of claim 21, wherein the M-RTS frameincludes a plurality of identifiers for identifying each of theplurality of wireless communication terminals.
 23. The base wirelesscommunication terminal of claim 21, wherein the first one or more bitsindicate index of the channel and the second one or more bits indicatethe index of the sub-channel.
 24. The base wireless communicationterminal of claim 21, wherein the processor is configured to transmitdata frames to the plurality of wireless communication terminal when apredetermined time elapses after receiving the CTS frame.
 25. The basewireless communication terminal of claim 21, wherein the processor isconfigured to transmit the M-RTS frame through a frequency bandincluding the primary channel having the minimum unit bandwidth.
 26. Awireless communication terminal comprising: a transceiver; and aprocessor, wherein the processor is configured to receive, by using thetransceiver, a M-RTS (Multiple-Request to Send) frame from the basewireless communication terminal, wherein the M-RTS frame is a mediumaccess control (MAC) frame and includes a plurality of channel vectorfields, wherein each of the plurality of channel vector fields indicatesinformation on an allocated sub-frequency band which is allocated to awireless communication terminal corresponding to each of the pluralityof channel vector fields among the plurality of wireless communicationterminals, wherein the allocated sub-frequency band allocated forcommunication between the base wireless communication terminal and atleast one of the plurality of wireless communication terminals after atransmission of the M-RTS frame, and transmit a Clear to Send (CTS)frame which is a response to the M-RTS frame to the base wirelesscommunication terminal, wherein bits of each of the plurality of channelvector fields are divided into a first one or more bits indicating alocation of a channel, among a plurality of channels, which includes theallocated sub-frequency band, and a second one or more bits indicating alocation and a size of a sub-channel corresponding to the allocatedsub-frequency band within the channel, wherein a number of the secondone or more bits is larger than a number of the first one or more bits,wherein the sub-channel is included in the channel.
 27. The wirelesscommunication terminal of claim 26, wherein the M-RTS frame includes aplurality of identifiers for identifying each of the plurality ofwireless communication terminals.
 28. The wireless communicationterminal of claim 26, wherein the first one or more bits indicate indexof the channel and the second one or more bits indicate the index of thesub-channel.
 29. The wireless communication terminal of claim 26,wherein the processor is configured to receive a data frame from thebase wireless communication terminal after transmitting the CTS frame.30. The wireless communication terminal of claim 26, wherein theprocessor is configured to receive the M-RTS frame through a frequencyband including the primary channel having the minimum unit bandwidth.31. An operation method of a wireless communication terminal comprising:receiving a Multiple-Request to Send (M-RTS) frame from the basewireless communication terminal, wherein the M-RTS frame is a mediumaccess control (MAC) frame and includes a plurality of channel vectorfields, wherein each of the plurality of channel vector fields indicatesinformation on an allocated sub-frequency band which is allocated to awireless communication terminal corresponding to each of the pluralityof channel vector fields among the plurality of wireless communicationterminals, wherein the allocated sub-frequency band is for communicationbetween the base wireless communication terminal and at least one of theplurality of wireless communication terminals after a transmission ofthe M-RTS frame; and transmitting a Clear to Send (CTS) frame which is aresponse to the M-RTS frame to the base wireless communicationterminals, wherein bits of each of the plurality of channel vectorfields are divided into a first one or more bits indicating a locationof a channel, among a plurality of channels, which includes theallocated sub-frequency band, and a second one or more bits indicating alocation and a size of a sub-channel corresponding to the allocatedfrequency band within the channel, wherein a number of the second one ormore bits is larger than a number of the first one or more bits, whereinthe sub-channel is included in the channel.
 32. The operation method ofclaim 31, wherein the M-RTS frame includes a plurality of identifiersfor identifying each of the plurality of wireless communicationterminals.
 33. The operation method of claim 31, wherein the first oneor more bits indicate index of the channel and the second one or morebits indicate the index of the sub-channel.
 34. The operation method ofclaim 31, further comprising receiving a data frame from the basewireless communication terminal after transmitting the CTS frame. 35.The operation method of claim 31, further comprising receiving the M-RTSframe through a frequency band including the primary channel having theminimum unit bandwidth.